Pages

Multiple sensors, and alternate statistical estimators, were tested for measuring canopy transmittance in four stands under a variety of sky conditions. On a given day, stand average transmittance estimates were insensitive to degree of synchronization of the sensors used to measure under-canopy and incoming radiation. In comparisons to periodic measurement of incoming...

The signal strength of a biweight site chronology is properly viewed as an outcome of analysis rather than as a property of the forest-climate system. It can be estimated by the evenness of the empirical weights that are assigned to individual trees. The approach is demonstrated for a 45-year biweight chronology obtained from 40 jack pine (Pinus banksiana Lamb.) trees...

Abstract: Nutrient export coefficients are estimates of the mass of nitrogen (N) or phosphorus (P) normalized by area and time (e.g., kg/ha/yr). They have been estimated most often for watersheds ranging in size from 102 to 104 hect-ares, and have been recommended as measurements to inform management...

We investigated the influence of landscape factors on the distribution and life stage stability of coastal tree species near the northern limit of their ranges. Using data from 1465 forest inventory plots, we estimated probability of occurrence and basal area of six common conifer species across three broad latitudinal regions of coastal Alaska. By also comparing...

For 1.5 to 2.5 billion people in the world, clean water is a critical issue (Lepkowski 1999). In the U.S., it is estimated that 90% of all Americans live within 10 miles of a body of contaminated water (Hogue, 2000). The development of filters to clean our water supply is big business. It is estimated that global spending on filtration (including dust collectors, air...

Changes in forest ecosystem function and condition arise from changes in forest fragmentation. Previous studies estimated forest fragmentation for the continental United States (US). In this study, new temporal land-cover data from the National Land Cover Database (NLCD) were used to estimate changes in forest fragmentation at multiple scales for the continental US....

Within-grade variability in mechanical properties for visually graded lumber has led to increased deployment of nondestructive testing (NDT) methods, even though the relationships between static bending and NDT-predicted values are often highly variable. Dynamic modulus of elasticity (MOEdyn) was measured using two acoustic velocity instruments and one transverse...

Healthy riparian ecosystems in arid and semi-arid regions exhibit shifting patterns of vegetation in response to periodic flooding. Their conditions also depend upon the amount of grazing and other human uses. Taking advantage of these system properties, we developed and tested an approach that utilizes historical Landsat data to track changes in the patterns...

Growth and longevity of freshwater mussels (Unionida) are important for defining life-history strategies and assessing vulnerability to human impacts. We used mark?recapture and analysis of shell rings to investigate age and growth of the hyriid, Westralunio carteri, at 5 sites in southwestern Australia. We tested the utility of the in situ marker...

Biodiversity, although recognized as encompassing several levels of biological organization, is often thought of as species diversity. Three diversity estimates were calculated for the conterminous United States using satellite data acquired from the Advanced Very High Resolution Radiometer (AVHRR): land cover richness, vegetation richness, and vegetation clustering....

Forest health analysts seek to define the location, extent, and magnitude of changes in forest ecosystems, to explain the observed changes when possible, and to draw attention to the unexplained changes for further investigation. The data come from a variety of sources including satellite images, field plot measurements, and low-altitude aerial surveys. Indicators...

Many of today's environmental problems are in scope and their effects overlap and interact. We developed a simple method to provide an integrated assessment of environmental conditions and estimate cumulative impacts across a large region, by combining data on land-cover, population, roads, streams, air pollution, and topography. The integrated assessment...

A survey of numerous field studies shows that nitrogen and phosphorous export coefficients are significantly different across forest, agriculture, and urban land-cover types. We used simulations to estimate the land-cover composition at which there was a significant risk of nutrient loads representative of watersheds without forest cover. The results suggest that at...

Forty-five-year ring width index chronologies were estimated by five mean-value functions applied to 183 ring width series from four similar sites. The effects of autocorrelation on the comparisons among mean-value functions were explored by fitting box-Jenkins models to individual-tree index services prior to pooling (prewhitening), and to the pooled chronologies...

The chemical compositions of loblolly pine (Pinus taeda L.) bark samples from two industrial sources were determined for whole bark as well as the inner and outer bark components. Differences in extractive contents of the whole bark samples were primarily attributed to the different debarking methods which afforded different proportions of inner and outer bark....

We examined slash from thinning treatments in a 21-year chronosequence of young-growth stands in southeast Alaska to determine the strength and persistence of slash effects on two key features of deer habitat quality: forage availability and deer mobility within thinned areas. We describe the main deterioration processes and their dynamics over time. We measured wood...

USDA Forest Service Forest Inventory and Analysis plot information is widely used for timber inventories, forest health assessments, and environmental risk analyses. With few exceptions, true plot locations are not revealed; the plot coordinates are manipulated to obscure the location of field plots and thereby preserve plot integrity. The influence of perturbed plot...

Air pollutants pose a risk to forest health and vitality in the United States. Here we present the major findings from a national scale air pollution assessment that is part of the United States? 2003 Report on Sustainable Forests. We examine trends and the percent forest subjected to specific levels of ozone and wet deposition of sulfate, nitrate, and ammonium....

Scientists and environmental managers alike are concerned about broadscale changes in land use and landscape pattern and their cumulative impact on environmental and economic end points, such as water quality and quantity, species habitat, productivity, erosion potential, recreational value, and overall ecological health (Rapport et al., 1998). They also are interested...

Spatially explicit identification of changes in ecological conditions over large areas is key to targeting and prioitizing areas for environmental protection and restoration by managers at watershed, basin, and regional scales. A critical limitation to this point has been the development of methods to conduct such broad-scale assessments. Field-based methods have...